Power pressure intensifier



April 15, 1952 E. A. ROCKWELL POWER PRESSURE INTENSIFIER 4 Sheets-Sheet 1 Filed Jan. 24, 1945 INVENTOR Edward JLRoc/nwell ATTORN Y April 15, 1952 E. A. ROCKWELL 2,593,394

POWER PRESSURE INTENSIFIER Filed Jan. 24, 1945 4 Sheets-Sheet 2 INVENTOR I Edward filioc/vwell April 15, 1952 E. A. ROCKWELL P OWER PRESSURE INTENSIFIER 4 Sheets-Sheet 15 Filed Jan. 24, 1945 INVENTOR Edward A..R0c/rwelZ AT RNEY April 15, 1952 E. A. ROCKWELL 2,593,394

POWER PRESSURE INTENSIFIER Filed Jan. 24, 1945 4 Sheets-Sheet 4 INVENTOR Edward vQRoc/cwefl ATTORNEY Patented Apr. 1 5, 1952 Edward A. Rockwell, Cleveland, Ohio Application January 24, 1945, Serial No. 574,325

My invention relates particularly to power units, etcQconstructed so as to simplify the same,

which may be used to perform work, as, for instance, in the operation of the difierent parts of automotive vehicles, such, for example, as brakes, etc. L

The present application is a continuation in part of my copending application upon Pressure .Fluid Operated Pressure Intensifier, Serial No.

539,584giiled June 9, 1944.

perform work, but which is applicable especially to the operation of brakes in automotive vehicles, as, for. instance, automobiles, airplanes, etc. The object of my invention is also to provide power units of the above character in which some of the piping and valve structure may be eliminated. Another object is to provide an effective means The object of my invention is to provide a sim- ,plifiedpower unit which may be used for the operation of any desired element to be moved to for obtaining liquid compensation in a hydraulic system. A further object is to locate the valves of the unit at the same end thereof. Another object is to avoid valves in the power plunger.

. Further objects of my invention will appear from the detailed description of the same hereinafter. Whilemy invention is capable of being carried out in m any difierent ways, I have shown only certain forms thereof in the accompanying drawings, in which:

Fig l is a longitudinal section of a form of my power unit, shown diagrammatically, utilizing power piston;

Fig. Z'is a diagrammatic longitudinal section of another form of my power unit, using a diaphragm for application of power;

Fig. 3 is a diagrammatic longitudinal section of another modification of the power unit; and

Fig. 4 is .a diagrammatic longitudinal section of a further modification of my invention, having an inlet coaxial with the power plunger.

In the drawings, referring first to Fig. 1, I

, have provided a pedal I carried by a pedal lever 2 mounted on a pivot 3 carried by the chassis of an automobile. The lever 2 has a pivot 4 for a link 5 which is connected to a piston rod 6 having a piston 1 operating in a master cylinder 8. The

master cylinder has the usual reservoir 9 provided with/a vented filling cap I0 and a liquid compensation port II to supply liquid to the cylinder in the retracted position of the piston I.

The cylinder 8 is connected by a pipe I 2 to an inlet opening l3 in a casing M which is provided with a chamber l5 which connects with a pasi 'sageway I6 in a monitor piston l1 screw-threaded 16 Claims. (01. co -54.5)

into the side' of the casing I l. The passageway I6 communicates with a chamber l8 in the end of a hollow plunger I9 having a piston 20 which is provided with a leather sealing ring 2l fitting within a power cylinder 22. The plunger l9 has an internal annular seal 23. The plunger [9, also, has a rubber seal 24 carried by a cylinder 25. Beyond the right-hand end of the plunger I9 there is the hydraulic pressure-increasing cylinder 25 forming a part of the cylinder 22, having a liquid compensation reservoir 26 with a liquid compensation port 21, the cylinder 25 being connected by an outlet and a pipe 28 to branch pipes 29 and 39 leading to brake cylinders 3i and 32, respectively, which are connected, respectively, to brake shoes 33 and 34 on the rear wheels of the automobile. It will be understood, of course, that similar branch pipes and brake cylinders may be connected to the pipe 28 leading to front 'lower end the plunger 31 passes through a seal .4! in the casing I4 and contacts with a valve stem 42 on which there is carried a vacuum valve '43 adapted to seat on a valve seat 44 carried by a screw ring 45 having a series of internal flutings 46 for guiding the valve stem 42. The valve ring 45, furthermore, is screw-threaded to an air inlet valve member 41 normally pressed upwardly by a helical spring 48 seated within a spacing ring 49 secured by screws 50 to the valve casing member 41..

I4 and to a cap 5| by screws 52. Between the spacing ring 49 and thevalve casing 14 there is clamped, at its outer periphe y, a. diaphragm 53, the inner periphery thereof being clamped between the screw ring 45 and the air inlet valve It will be noted, furthermore, that the air inlet valve member 41 has a flange valve 54 which cooperates with a valve seat 55 on the spacing ring 49 and that the saidvalve member has a series of longitudinal passageways 5B acting to permit the passage of air. On the stem 42 there is-a shoulder 51 supporting a helical spring 58, the lower end of which is capable of being compressed as it is supported by an adjusting screw 59 screw-threaded in the cap 5|. The cap 5!, furthermore, is connected by a pipe 60 toan inlet 6| leading to a chamber 62 in the power cylinder 22. Also; within the spacing ring 49 there is a chamber 53 having an air inlet pipe 64 covered by a cap 55 supported therefrom by a spider ring 65 having air inlet apertures 01. The valve casing I4 has a vacuum chamber 53 which communicates by a port 69 with a pipe which is connected to the manifold of the automobile engine. Also, said valve casing has a vacuum pipe connection 1! leading from a port 12 in the valve casing I4 to a port13 in a vacuum chamber 14,at the right of the piston 20, in which there is located a helical spring 15 supported at one end by the cylinder 22 and at the other end against a ring 16 which is pressedby the spring 15 against the leather washer 2I to retain it in place. v

In the form of my invention as shown in Fig. 2, I have provided the usual pedal 11 mounted on a fixed pivot 18 having a pivotal connection 19 by a link 80 to a piston rod BI in a master cylinder 82 which is connected by a hydraulic line 83 toan inlet 84 on a combined plunger and dia- 'phragm housing 85. The housing 85 has a flange 85enclosed by a' U-shaped split'ring 81, the ends ofwhich have a bolt 88 pulling them together in a" peripheral direction. Said ring 81, L also, "clam'ps'a flange 80 of a diaphragm housing 90 'which 'has .aconnection 9| to any desired source To vacuum. 'Integralwith the diaphragm housing 90 there is acylinder 02 having a liquidgcom- I pensation' reservoir 93 and a liquid compensation passageway 94, having an outlet 95 connected by ja' hydraulic 1i'ne95 to wheel cylinders 9170i front I and rear wheels 98 on the automobile. The cylinder 92 receives one end of 'a rearwardly-directed plunger 99 which is clamped to the middle portion of a flexible diaphragm I00 by a clamping'plate IOI and screws I02. The outer periph- "eryof the diaphragm I00 is clamped between the flanges 85 and 89 .by the clamping ring 81. In-

tegral with theplunger 99l and at the forward .n'd thereof, there is a smaller plunger I03 which slides within a sleeve I04 carried by the cylinder 85 The; forward end of the sleeve I04 has 'an apert'ure I05 which is connected by means of a chamber I06 to'the hydraulic inlet port 84. The "j sl'eeve I0,4" serves asamovable' operating means for a projection I01 on a valve-operating lever I08 which "has a pivotal suppOrt I09 by means of ears IIO on the plunger'90 at one side of the f plunger I03. At one endthe lever I03 has a resistingspring I II I providing a support from the 1 plunger 99'and near itsot-herend carries anadfjustable screw-threaded stop I I2. At this end of .ffthe leverI08thereis a pivotal connection I I3 to a valve operating rod I I4 connected to a vacuum "inletvalve II5 cooperating with a valve seat IIB ion a subsidiary diaphragm II1 which is connected to an air inlet valve sleeve II8 having an 'air inletvalve II9 for cooperating with an air "valve seat I20. A relatively resistant, lever actu-' ated, spring I2I is provided for normally seating the air valve II9 on its seat I20. It willbe un- ;derstood that this vacuum and air valve conis tructi'on is the same as shown ,infde'tail in Fig. 1 described hereinabove. The said j spring I 2 I T is located in an air chamber I22 which leads to'a passageway I23 in the plunger 99 which ends in a nipple I24 connected by afiexible conduit I25 [to an air inlet'port I26. r p

1 The modification shown in Fig. 3 is constructed the same as the modification shown in Fig. '2, except thatin this instance a piston I21'is' sho'wn fitting within a cylinder I28 and except for the arrangement of the valves. In this instance I have provided on the cylinder I a" sinall'r cyloperating; rod I36 on a valve I31 which seats against avalvefseat I38 within the piston I21 which is connected by a passageway I39 to the j'chamber within the cylinder I28 at the left of ,the pistonl21. A spring I40, supported on a seat I4I, normally presses the valve I31 to the right the piston :21.

so as to opena port I42 leading from the chamber at the left of piston I21 to the right face of The said valve I31, thus, normally conveys the vacuum from the left to the right face of the piston I21. The lower end of the valve-operating lever I33 has a pivot I43 connecting it to a valve-operating rod I44 on an'air inlet valve I45 which is normally pressed against a valve seat I45 by a spring I41 carried by a recess I48' in a chamber I49 in the piston I21. The said chamber I49 has a port I50 connecting it to the right face of the piston I21 and has a passage I5I leading to a nipple I52 connected by a rubber tube I53 to a vent, as shown in the modification in'Fig. -2. This modification of my invention, shown in Fig. 3, thus, receives 'onthe manual means a reactionfrorn the air pressure admitted to the right side-of the piston I21 according to "the hydraulic reaction from the hydraulic liquid applied by the power unit to the wheel cylinders inasmuch as said admitted air pressure acts on the left end of the plunger I30 and hence'produces a feel by the master cylinder liquid, but onaccount of the manner in which the valves are mounted, the manual means does not receive any substantial reaction from the modulating valve-operating mechanism as the admitted air pressure tends to move the valve lever I33 away from the plunger I30.

In Fig. 4 I have shown diagrammatically a modified form' of my invention which is constructed just like'the embodiment shown in Fig. 2, with the following differences, however. In this instance I have'provided a cylinder I54 having reciprocable therein a piston I55 on which i there is supported, by means of a spring I56, a valve lever I51 just like the valve operating memberin- Fig. '2 and which is arranged tofoperate a valve mechanism constructedthe same as the inlet and outlet valve mechanism for the vacuum and air as shown in Fig. 2. Resting against the end of the lever I51, in order to opwhich is on the end of a hollow plunger I63 passing'through a'packing I64 in the cylinder I59.v The hollowplunger I63 thus passes into the cylinder I54 so that the air is conveyed throughja longitudinal passageway I56 therein to an air j chamber I61 inthe piston I55, so as to be-led "therefrom by means of a radial passageway I68 to the valve mechanism operated by the lever I51, in-the same" manner as shown in Fig. 2.

In the embodiment of my invention shown in Fig. 1,-when manual pressure is applied to the edal I, .t:he master cylinder .8 supplies the fluid findertressure uranium-"pi e I2 to the inlet Also, in this instance, there.

I3, where, also, the liquid passes through the apertures 36 adjacent to the stop 35. The liquid, thus, under pressure from the piston I, produced by the pedal I, acts in the chamber I8 on the end of the means I9 to move the piston 29 so as to force the liquid out of the cylinder 25. The liquid passes from the cylinder 25 and thence through the pipe 28 to the brake cylinders 3| and 32, thus setting the brakes. Upon the further increase of the manual pressure the plunger 31 is moved forwardly against the compression of the spring 58, by the hydraulic pressure from the apertures 36, thus moving the vacuum outlet valve 43 into closed position, followed by the opening of the air inlet valve 54 which admits air from the pipe 54 past the valve 54 into the pipe 69 and thence into the chamber 62 in the power cylinder 22. The pistonIB, having been previously submerged in a vacuum, is now moved to the right by the air pressure in the chamber 62, thus moving the end of said piston into the cylinder 25 and producing an intensified pressure which is supplied by the pipe 28 to the brake cylinders 3| and 32. This application of the intensified pressure is, thus, controlled in modulating amounts by the operation of the valves 43 and 54, which are self-lapping so that they are both closed in changing from a position in which both valves are closed to a position where more air is admitted to apply greater braking force, or to a position where more vacuum is admitted to apply a lessened braking force. Throughout the application of "manual force or intensified pressure from the cylinder 25 there will be a coordinate feel sensed by the operator on the pedal I, according to the amount of braking force applied. Also, in this form of my invention there is provided a coordination of the travel of the pedal with the amount of travel of the brake-operating elements by reason of the monitor chamber I8, for the reason that as the piston I9 moves towards the right a coordinate amount of fluid is drawn into the chamber I8, so that the operator of the pedal I not only has a feel, but also senses the change of position which is coordinate to the amount of braking pressure and intensified pressure liquid supplied to the brakes. In this construction it will be noted that all the valves are conveniently located on one end closure for the power cylinder. Also, in this instance, the reaetionis felt on the manual means from both the modulating valves and the airpressure at the right of the diaphragm I99 according to the hydraulic power pressure exerted on the brakes.

In the operation of the power unit shown in Fig. 2, when the manual pressure liquid delivered by the master cylinder 82 is received in the inlet 84, the liquid, under pressure from piston 99, passes directly through the pipe 96 to the brake cylinders 91 from the cylinder 92. The wheel brakes will, thus, be given their initial movement in this manner, as, for example, to set the brakes and perhaps apply some of the braking pressure. When the manual pressure in the pipe 83 is increased, however, the plunger 99 will be moved further. This forward movement of the plunger 99 is brought about by the movement of the sleeve I94 forwardly by the master cylinder acting on the restricted effective pressure area at the right hand end of the sleeve I94, thus moving the valve lever I98 against the force of the spring III and the spring I2I to seat the vacuum valve H5, H6, followed by the unseating of the air inlet valve H9, I29, which admits air from the air port I26 to the right face of the diaphragm I99, resulting in the movement of the plunger 99 towards the left and thus also exerting the reaction force on the left end of the plunger I94 and hence produces a feel by the master cylinder liquid, in addition to a reaction from the modulating valves acting, by means of the lower end of the lever I91, on the plunger I94. In any position of rest of the foot thus attained on the pedal 11, the air valve H9, I29 will become seated in lapped position with regard to the valve I I5, I I6. Further forward movement. due to increased manual pressure, will again unseat the air valve H9, I29 toapply further movement of the plunger 99 towards the left so as to exert a higher braking effort on the braking cylindersBI. In the release of the pressure from the brakes, the air valve H9, I29 will close and the vacuum admission valve H5, H9 will open, thus restoring the vacuum to both sides of the diaphragm I99. During this operation of applying hydraulic liquid under power pressure to the wheel cylinders 91, the reaction on the manual means will be due only to the amount of air pressure exerted on the right face of the diaphragm I99 by the operation of the modulating valve means and owing to the modulating valve being mounted on the diaphragm III.

In the operation of the form of my invention shown in Fig.3, the operation is the same es-- the valve device acting on the power piston, and the reaction exerted on the manual means to provide a feel in this instance is the reaction from the air admitted to the right of the piston I2'I according to the hydraulic pressure liquid, for instance in the pipe 99, applied by the power derived from the piston I2'I of the power unit on the brake cylinders. Also, it will be noted that the valve operating sleeve I39 operates a type of valve mounting which does not receive a reaction from the air pressures admitted, to any substantial extent.

The operation of the modification of my invention shown in Fig. 4 is the same as the operation of the form of the apparatus shown in Fig. 3, with the exception that, in this instance, the reaction to provide the feel is through the valve means and the air is admitted to the apparatus from the air inlet port IBI at the forward end of the unit through the passageway I66 inthe plunger I63 and from the chamber I61 to the modulating valve apparatus which is mounted on the piston I55 and which is controlled by the plunger I58 under the influence of the manual pressure exerted on the master cylinder piston to be applied to the liquid received by the hydraulic line I99 leading from the master cylinder.

While I have described my invention above in detail, I wish it to be understood that many changes may be made therein without departing from the spirit-of the same;

I claim:

1. A power unit, comprising a connection on the power unit adapted to be connected to a source of pressure differing from the atmospheric pressure, a power motor having a movable wall, a chamber containing said wall, a hydraulic plunger operated by said wall, said plunger being provided with a chamber in which one end of said plunger operates, a valve mechanism carried.

geese-9e 7" by the rihie for controlling the application of I said pressure to said motor, hydraulic means for receivin'g' pr'essure from a master cylinder, having a hydraulic connectionto the opp'os'ite'end'o'f said plunger for moving theplunger so that a reactionieexerted from the appliedpower to said-master cylinder' hydraulic connection, said master cylinder "being provided for suppling' to the unit =hy'- draulic fluid to control the valve mechanism; a

valve operating 'sleeve located around a portion of said plunger, an element adapted to perform work, '"and a hydraulic connection from said element to the plunger-chamber having a liquid compensating reservoir provided with a compen sation pcrtcoopratingwith saidotherend of plunger operated-by said w'alhsaid plunger being provided with a chamber in which it'operates, a valve mechanism carried by the unit on ahemovable wall outside of said pluhgerfor controlling the ap'plic'ation of said pressure to said 'mot'or, hydraulic means for'receiving pressure from a master cylinder for supplying to the unit hydrauli'c fluid to control the valve mechanism, a valve operating plunger movable relative to the saidplunger and located away from said plunger chamber, an element adapted to perform work, and a hydraulic connection from said element to the plunger chamber having a liquid compensatin'greservoirprovided with a compensation port at therear of the plunger chamber uncovered-by said plunger when retracted.

A power'unit, comprising a connection on the power unit adapted to be connected to a source of pressure diifering from the atmospheric pressure, a power motor having a movable wall, a -cha mber containing said wall, a hydraulic plunger operated by said wall, said plunger being provided with a chamber in which one end of said'plunger operates, a valve mechanism carried by the unit for controlling the application of said pressure to said motor, an airinle't on the unit'connectedto the valve mechanism, hydraulic' me'a'n's forreceiving pressure from a master cylinder, havinga hydraulic connection to the opposite end of 'said plunger for moving the plunger'so that a reaction is exerted jfromthe applied power to-said master cylinder hydraulic connection, said master cylinder being. provided for su'ppl'ying to the unit hydraulic fluid'to con- *trol the valve mechanism, a -v'alve operating sleeve located around a portion of said plunger, anoutlet adapted to be connected to a fluid pres-- sure delivery-dine for supplying a fluid motor, and 'a'. hydraulic compensating reservoir provided with a-compensation port cooperating with said mechanism, hydraulic'means forreceiving pres sure-near a mastersc'ynnder f or supplying tb the unit hydraulic fluid to control the "valv lfl'hd n'ism, a Valve operatin -piunger movabie reiauve t0 the-saidplunger and iocatea away rrom said plunger chamber, an outlet adapted to be 1 connected to a Y fluid pressure delivery line' fo'r supplying a fluid motor hydraulically connected to said plunger chambeaanaa hydraulic compensatill'g reservoir provided With- 'a 1 compensation port at the rearo'f the-plunger chamber uncovered by sai d plunger when retracted;

'5.- A power unit; comprising a connection-on the' poweru'nit adapted tobe connected to "a source of pressure difiering from the atmospheric pressure, a power motor, having a 'mbvaple'wali, a chamber containing said wall, ahydraulic plunger operated by 'said -wall,' -s"aid mungenbemg provided-with achambera waive mechanism carried by the unit io con"- trbllin g th applicatioii 0f sear-pressure to said motor; anair inlet in theunit'h'aving a plunger located in the air inlet connected to the movable wall, hydraulic means "for --receiving pressure from a master cylinder for supplying tothe unit hydraulic fluid to control the valvemeehanism, an outlet adapted to be connected to a flui"d;pressure delivery line for supplying a fluid motor, and a"hydrauliccompensating reservoir provided with a compensation port cooperating witl'i said first-mentioned plunger.

source of pressure differing from theatrnospheric pressure, a power'm'otor, having amovable 'Wall,

a chamber containing said wall,- a hydraulic plunger operated by'- said wall, said plunger being provided with a chamber in which it 'operates,

avalve mechanism carried by the unitorithe movable wall for controlling the appli'cation o'i said pressure to said motor, an air inlet in the unit'h'aving a plungerlocated' in thair --inlet connected to the movable wall, hydraulic means forreceiving pressure from amaster cylinder-for supplying to the unit hydraulic fluid to control the valve mechanism; an outlet adapted to "be connected to a fluid pressure delivery line for supplying a fluid -motor-, and a hydra'ulic c'ornpensati ng reservoir provided with a compensation port cooperating with "said first mentioned plunger. I

7. A power unit, comprising afconnecnon cn the power unit adapted to be connected tc'- a source of pressure differing from the atmospheric pressure, a power motor, haying a movable'wall, a chamber containing s'aid'wall, a hydraulic I plunger operated by said wall, saidplunger being provided with a chamber in which it operates, a valve mechanism "carried by; the unit" outside of said plungerfor controlling the application of said pressure to said motor, an 'airinlet on the unit having "a flexible tube connected to the valve mechanism, hydraulic means forreceiving 'ressure'from a master -cylinder for supplying o the unit hydraulic fluid to c'ontrol thevalve' rriechanism, a valve operating piung ermavens-relative to thesaid plungeiand located away frqrasaid plunger chamber, an outlet adapted'to be connectedto a fluid pressure delivery line fo-r' s'upplying a fluid "motor,- and a hydraulic compensating reservoir provided with a-compens'atiomport cooperating with said plunger.

'8; A power unit, comprising aconnectiondn the power unit adapted to be connected toa source of pressure difiering from the atmospheric pressure,- a power motor, having a-mo'v'able wan, 9r chamber" containing- Said Wall} 113}Chittilitt whicliripperates,-

9 H plunger operated by said wall, said vplungerloeing provided with a chamber in which it operates, a valve mechanism carried by the unit on the movable wall outside of said plunger for controllingthe application of said pressure to said motor, an air inlet on the unit having a flexible tube, connected to the valve mechanism,hydraulic means for receiving pressure from a master cylinder for supplying to the unit hydraulic fluid to control the .valve mechanism, a valve operating plunger movable relative to the said plunger and located away from said plunger chamber, an outlet adapted to be connected to a fluid pressuredelivery line for supplying a fluid motor, and a hydraulic compensating reservoir'provided with a compensation'port cooperating with said plunger. 3, 9. A, pQWer unit,- comprising a connection on the power unit adapted to be connected toa source of pressure differing from the atmospheric pressure, a power motor, having a movable wall, a chamber containing said wall, a hydraulic plunger operated by said wall, said plunger being provided with a chamber in which it operates, a valve mechanism carried by the unit on the movable wall outside of said plunger for controlling the application of said pressure to said motor,

hydraulic means for receiving pressure from a master cylinder for supplying to the unit hydraulic fluid to control the valve mechanism, an element adapted to perform work, a hydraulic connection from said element to the plunger chamberhaving a liquid compensating reservoir provided with a compensation port at the rear of the plunger chamber uncovered by said plunger when retracted, and a valve operating piston movable relative to said plunger and located away from the said plunger chamber between the master cylinder and the valve mechanism.

10. A power unit, comprising a connection on the power unit adapted to be connected to a source of pressure diifering from the atmospheric pressure, a power motor, having a movable wall, a chamber containing said wall, a hydraulic plunger operated by said wall, said plunger being provided with a chamber in which it operates, a valve mechanism carried by the unit on the movable wall outside of said plunger for controlling the application of said pressure to said motor, an air inlet on the casing connected to the valve mechanism, hydraulic means for receiving pressure from a master cylinder for supplying to the unit hydraulic fluid to control the valve mechanism, an outlet adapted to be connected to a fluid pressure delivery line for supplying a fluid motor, a hydraulic compensating reservoir provided with a compensation port at the rear of the plunger chamber uncovered by said plunger when retracted, and a valve operating piston movable relative to said plunger and located away from the said plunger chamber between the master cylinder and the valve mechanism.

11. A power unit, comprising a connection on the power unit adapted to be connected to a source of pressure differing from the atmospheric pressure, a power motor, having a movable wall, a chamber containing said wall, a hydraulic plunger operated by said wall, said plunger being provided with a chamber in which it operates, a valve mechanism carried by the unit on the movable wall for controlling the application of said pressure to said motor, hydraulic means for receiving pressure from a master cylinder for supplying to the unit hydraulic fluid to control the valve mechanism, an element adapted to perform work, a hydraulic connection from said element I control the valve mechanism, an outletadapted to the power unit having a liquid compensating reservoir provided with a compensation port co-' operating with said plunger, and a valve operating piston around a portion of the hydraulic plunger located between the master cylinder and the valve mechanism on the other side of the movable Wall from said plunger chamber.

12. A powerunit, comprising a connectionon the power unit adapted to be connected to a source of pressure differing from the atmospheric pressure, a power motor, having a movable wall, a chamber containing, said wall, a hydraulic plunger operated by said wall, said plunger being provided with a chamber in which it operates, a valve mechanism carried by the unit on the movable wallfor controlling the, applicationof said pressure to said motor, an air inlet on the casing connected to the valve mechanism, hydraulic means for receiving pressure from a master cylinder for supplying to the unit hydraulic -fluid to to be connected to a fluid pressure delivery line for supplying a-fiuid motor, a hydraulic compensating reservoir providedgwith a compensation port cooperating with said plunger, and avalve operating piston around a portion of the hydraulic plunger located between the master cylinder and the valve mechanism on the other side of the movable wall from said plunger chamber.

13. A power unit, comprising a connection on the power unit adapted to be connected to a source of. pressure. difiering fromthe atmospheric pressure, a power motor, having a movable wall, a chamber containing said wall, a hydraulic plunger operated by said wall, said plunger being provided with a chamber in which it operates, a valve mechanism carried by the unit on the movable wall outside of said plunger for controlling the application of said pressure to said motor, hydraulic means for receiving pressure from a master cylinder for supplying to the unit hydraulic fluid to control the valve mechanism, an element adapted to perform work, a hydraulic connection from said element to the power unit having a liquid compensating reservoir provided with a compensation port cooperating with said plunger, a valve operating lever, and a valve operating piston movable relative to said plunger and located away from the said plunger chamber between the master cylinder and the valve lever.

14. A power unit, comprising a connection on the power unit adapted to be connected to a source of pressure difiering from the atmospheric pressure, a power motor, having a movable wall, a chamber containing said wall, a hydraulic plunger operated by said wall, said plunger being provided with a chamber in which it operates, a valve mechanism carried by the unit on the movable wall outside of said plunger for controllin the application of said pressure to said motor, an air inlet on the casing connected to the valve mechanism, hydraulic means for receiving pressure from a master cylinder for supplying to the unit hydraulic fluid to control the valve mechanism, an outlet adapted to be connected to a fluid pressure delivery line for sup-plying a fluid motor, a hydraulic compensating reservoir provided with a compensation port cooperating with said plunger, a valve operating lever, and a valve operating piston movable relative to said plunger and located away from the said plunger chamber between the master cylinder and the valve lever.

15. A power unit, comprising a connection on the power unit adapted to be connected to a source of pressure difiering from the atmospheric pressure, -a-power motor, having a movable-lwalh a chamber containing said wall a hydraulic. plunger operated by said wall, said plunger being:

provided with a chamber in which it operates, a

valve-mechanism carried by theunit onithe mov able waH-forcontrolling. the-application of said pressure to said motor, hydraulic means for recei-ving pressure from a 'mas'tercylinder for supplying to the unit hydraulic fluid to control the valve: mechanism, an element adapted to perform the-power unit adapted to be connected to a source of pressure differing from the atmospheric pressure, -a power motor, havinga movable Wall, a chamber containing said wall, I a hydraulic plunger o'p'erated by said Wall, saidplunger being provided with a chamber in-Which it operates, a valvemechanism carried by-the' unit onthe-movable -wall for controlling the application of said pressure to said" motor, an air inlet onthe casing connected to the valve mechanism, hydraulic meansrion:receivingrpre u 1 1,5 master Wk inder" for pp ying to. the innit h erauncnumto control .the rvalve mechanism,.f'an :elen'rent adaptedhto perform work, a hydraulicv compensating reservoir provided with .a compensation port cooperating with said plunger, a valve operating lever, and .azvalve ioperating .pis'ton located between thev master cylinder and the valve lever, .s'aid hydraulic plunger having its Tends extending'to opposite sides of themovablewall, an end :beingzconnected hydraulically 'to the mastercylinder and. the other end connectedihydranlica-llytto said element .byasaidmldngex: chamber;

' EDWARD "A; ROCKWELL.

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